The present invention relates to apparatus for manipulating workpieces, especially for manipulating workpieces having pairs of substantially plane parallel surfaces. More particularly, the invention relates to improvements in apparatus for supporting, locating and transferring workpieces for treatment at a plurality of stations, such as successive stations of a surface grinding machine whose tools serve to treat each of the plane parallel surfaces on metallic valve heads or other types of workpieces having pairs of spaced parallel surfaces.
Heretofore known techniques of manipulating workpieces in a multi-station surface grinding machine, in another machine tool or in a production line which serves to treat several discrete surfaces of a series of workpieces, especially plane parallel surfaces of flat workpieces, are cumbersome and time-consuming, mainly because each workpiece must be transferred by hand or by a mechanical transfer element from a first carrier which supports the workpieces in such a way that one surface of each supported workpiece is accessible and a second carrier serving to support each workpiece with a view to expose the other surface for treatment by one or more tools. As a rule, such rechucking of workpieces necessitates the presence of at least one attendant who removes successive workpieces of the series from a first carrier and transfers the removed workpieces to the next-following carrier (with or without inversion of workpieces during transfer). Therefore, machine tools or production lines which are used for such treatment of workpieces having pairs of plane parallel surfaces cannot form part of or constitute fully automated production lines because the treatment of workpieces in machine tools which have tools serving to remove material from two plane parallel surfaces of each workpiece is time consuming and, consequently, the installation of such machine tools in a production line would necessitate a slowdown or intermittent operation of each other machine in the respective production line. A surface grinding machine often subjects each surface of a workpiece to be treated to several treatments such as preliminary (coarse or rough) grinding and a secondary (final or precision) grinding. The carriers which support, locate and transfer the workpieces between successive stations may constitute so-called plate chucks which are movable, in their entirety, between neighboring stations or which include portions adapted to move successive workpieces from a preceding station to the next-following station.